The goal is to collect innovative data on expectations, randomized incentive payments and sexual behaviors, and to analyze the adaptation in sexual relations, household dynamics, and information-seeking to variation in (i) respondents' knowledge about their own health status, (ii) expectations about infection risks, STI/HIV prevalence, and risk-taking behaviors, and (iii) randomized direct monetary incentives for participating in voluntary counseling and treatment (VCT) and for maintaining a HIV negative status. The proposal takes advantage of the Malawi Diffusion and Ideational Change Project (MDICP) that collects an unusually rich combination of panel survey data (1998, 2001, 2004, with a forthcoming funded wave in 2006), qualitative data and biomarkers for HIV and other STIs. The specific aims include (a) the analysis of already collected data from an experimental design that offered randomized differential incentives for respondents to obtain their STI and HIV test results, (b) the collection of an additional round of survey and biomarker data in 2005 to create an experimental design that offers incentives for respondents to remain HIV negative and to measure expectations about behaviors and risks related to sexual health, (c) obtain repeated measurements of sexual activities during a 12 month period in 2005-06 using audio-computer assisted interviewing techniques, (d) investigate the patterns, formation and behavioral consequences of health related expectations, and (e) investigate the implications and effectiveness of direct monetary incentives rewarding a HIV-negative status for sexual relations, the adoption of STI prevention strategies, transition into marriage, divorce, subjective well-being and other STI/HIV-related behaviors and attitudes.